Gas analysis can be an important means for detecting the presence and concentration of certain chemicals in the gas and determining the meaning of the particular combination of chemicals present. In health care, for example, the presence of certain volatile organic compounds (VOCs) in exhaled human breath are correlated to certain diseases, such as pneumonia, pulmonary tuberculosis (TB), asthma, lung cancer, liver diseases, kidney diseases, etc. The correlations are especially evidential for lung-related diseases. In other applications, gas analysis can be used to determine the presence of dangerous substances incompatible with human presence, such as methane, carbon monoxide or carbon dioxide in a mine.
Current gas analytical systems still rely heavily on large and expensive laboratory instruments, such as gas chromatography (GC) and mass spectrometry (MS). Most of these instruments (mass spectrometers in particular) have operational characteristics that prevent significant reductions in their size, meaning that current gas analysis systems are large and expensive bench devices. In addition to being expensive and unwieldy, the large size of current gas analysis devices makes widespread use of these instruments impossible.
Since the conventional GC/MS are bulky in size and expensive, the equipment is usually located in the labs and breath samples must be collected in the laboratories or by other on-site means. Two approaches have been used for on-site breath collection. The canister breath collection is the most commonly used approach: breath is inhaled and collected into a pre-cleaned and pre-vacuumed bottle, and the bottle is then sent to a lab for analysis. Such canisters are very expensive and also require a very expensive cleaning system in order to re-use the canister. As a result, the breath test cost cannot be reduced due to very high cost in equipment and system setup. In another approach, instead of using a canister, a trap is used as an alternative on-site breath collection: the trap is located in a breath collection system, which monitors the amount of breath and condition during collection. The trap is then removed and then sent to lab for analysis using similar gas analysis equipments for the canister approach. The trap approach eliminates the requirement of expensive cleaning tools, but the trap collection system itself can be more expensive than the canister. Both breath collection and analysis approaches requires the breath collection on-site and then the samples are sent back to labs for analysis, which is time-consuming and very expensive.
Exhaled breath contains >90% humidity. When the moisture is collected together with gases/volatile organic compounds (VOCs) from breath and then directly injected into a gas analysis system, any significant amount of moisture will drastically reduce the analyzer sensitivity to chemicals/VOCs of interest. As a result, the system's detection limit becomes much worse than the case when there is no or low moisture present. The current approach in moisture removal for breath analysis is to extract the collected breath sample from the container, which is used to store breath from the subject. The sample is then extracted and injected into a front-end moisture removal equipment. The equipment cools down (condenses) the collected breath (including moisture) in a trap or tube to sub-zero Celsius temperature (by liquid nitrogen or dry ice) and then heats up the trap to separate moisture from other gases due to different boiling temperatures. There can be multiple stages of cryo-cooling and heating steps to remove moisture before gases/VOCs are transferred into a gas chromatograph/mass spectrometer (GC/MS) system for analysis. Such front-end equipment is massive in size and highly expensive (>$20,000).
The existing approach requires expensive equipment setup and is bulky in size as described above. The breath analysis is performed in multiple stages. Breath first is collected in canister, trap, or other container. The sample is then transferred to laboratory, where the moisture removal system (front-end system) and gas/VOC analysis system (e.g., GC/MS) are located. The gases/VOCs and moisture are then extracted from the sample to the front-end system for moisture removal before the gases/VOCs are fed into the analyzer (GC/MS). The equipment is expensive and not portable. Meanwhile, this breath collection and moisture removal procedure cannot be used for in-situ breath analysis.